Ashton Kutcher and Mila Kunis vistit Downton Abbey

Ashton Kutcher and Mila Kunis visited the set of 'Downton Abbey' to see the set of the popular series for themselves while on holiday in the UK

Ashton Kutcher and Mila Kunis visited the set of 'Downton Abbey'.

The showbiz couple - who are expecting their first child together - took a trip to the set of the ITV period drama during the making of the upcoming fifth series, which will kicks off this weekend.

Michelle Dockery - who plays Lady Mary Crawley in the hit programme - revealed that she was overjoyed when she found out that the Hollywood superstars would be coming down to the set, saying that they are huge fans of the show.

She told Radio Times magazine: "It's true Mila and Ashton came to visit us on set. They're big fans and were lovely!"

Ashton, 36, and Mila, 31, aren't the only celebrity fans of the show, however.

J.J. Abrams, who is famed for directing 'Star Trek' and the upcoming 'Star Wars: Episode VII', has previously declared his soft spot for the programme and last June, 'The Honourable Woman' actress Maggie Gyllenhaal expressed her desire to join the programme's cast.

Meanwhile, Michelle suggested it might be tough for new cast members joining 'Downton' because the original cast are all so close.

She explained: "We're all like a family on the show. Hugh Bonneville plays my father, which is weird because he's just my mate!"

The fifth series of 'Downton Abbey' begins on ITV at 9pm on September 21.